How do you know where to place the hotdog skewer? In other words, how do you determine the focal point…or do you just wing it? curious. I do a similar project but we use copy paper boxes. The kids have to keep the focus in the box. I think I want to modify the project and use your idea but tie more of the math to it. And is there a reason you chose the dimensions you used?

How to get the proper curve
A math specialist could make a program to print it up from a computer over a couple pages of paper
Then the rest of us could download the printouts, Print them and use them for templates

This is really neat. Will this solar hotdog cooker work in the winter when the temperature is below 40 degrees Farenheit. Hot dogs will cook on an asphalt parking lot in July or August on a piece of aluminum foil when the temperature of the asphalt has been heated to about 95 degrees Farenheit.

can also use a old satellite dish (the curved surface) covered with tin foil! even the gottom of a soda can will suffice for cooking experiments (a piece of hot dog). this is part of a survivalist kit!!